Introducing interactivity - vertical or horizontal?
While the Sonic palette available to games composers had improved, the music itself was still linear - playing alongside the action, rather than reacting to it. If a musical cue “pinged” when the player “ponged”, it was through serendipity, not design.
Adaptive scores - where the music players hear changes to match their gameplay - finally arrived in the 1990s.
There were two different, but complementary techniques.
The simplest is known as vertical re-orchestration. It works like an episode of Classic Albums where someone from Fleetwood Mac sits behind a mixing desk and shows off the isolated vocals for Go Your Own Way.
The game essentially takes control of the mixing desk, sliding the faders up and down depending on what’s happening on screen.
“It’s actually not that hard,” says Grant Kirkhope, who first used the trick on the Nintendo 64 games GoldenEye and Banjo-Kazooie.
He explains how he used Midi (Musical Instrument Digital Interface) files - a kind of digital sheet music - to create the illusion of music “following” the player around the game.
“In a Midi file, you get 16 channels, so you can have 16 instruments. So when I’d write the tunes, I’d find out what areas the design guys would want to have in each level, and I’d allocate a certain amount of instruments to each area,” says Kirkhope.
“Then we’d draw circles on the map, which the player can’t see, they’re hidden away, but when the player crosses that line, it signals to the audio engine to fade down, say, channels one, three and six and turn up two, four and eight.
“If you listened to the raw Midi file, you’d hear all the instruments at once, but the game controls which ones you hear at any one time.”
This technique is still used in games today - albeit with full orchestral recordings, rather than synthesised ones.
A more ambitious approach debuted on 1991’s The Secret Of Monkey Island 2 - a point-and-click adventure on the PC and Amiga.
Using the patented iMUSE (Interactive Music Streaming Engine) system, Michael Land and Peter McConnell created a branching musical score that could react dynamically to the player’s choices.
It’s apparent right from the start, when the ornately named protagonist, Guybrush Threepwood, wanders around the small town of Woodtick. Every time he enters a building or encounters a new character, the game introduces a variation on the main theme.
When he wakes up a group of sleeping pirates, for example, a jaunty accordion picks up the melody. As he walks away, the pirates’ theme ends with a flourish, before segueing seamlessly back to the overture.
The technique is called horizontal re-sequencing, and it works by putting “triggers” into the Midi files that contain the musical score. When a specific action occurs, the game jumps to the appropriate section of the song - as if the player is James Brown, telling the computer to “take it to the bridge”.
For the musician, though, horizontal resequencing presents a huge conceptual headache.
“You essentially have to take the core storytelling aspects of music composition and break them apart as if they’re all cards in a deck,” says Winifred Phillips, author of A Composer’s Guide To Game Music.
“You could be pulling any one of those cards at any particular time, and it has to be able to work on its own. So that unravels your brain as a composer. You’ve got to unlearn all the narrative aspects of composition that you’ve been taught.
“It’s challenging, it’s interesting, and it’s something composers and game teams are still exploring. And the more we explore, the more interesting gameplay becomes.”
No Man’s Sky: An infinite soundtrack
Taken to its most complex extreme, horizontal resequencing takes a grab-bag of musical components and puts them together like Tetris blocks as you play, creating an entirely unpredictable, dynamic score.
Glam-prog-ambient-techno genius Brian Eno took just that approach with The Shuffler - a piece of software that created a constantly mutating score for 2007’s ambitious-yet-flawed evolution adventure Spore.
A more recent application came in Hello Games’ space adventure, No Man’s Sky, which was released in 2016 for the PlayStation 4.